Vinyl acetate monomer (VAM) is a large-scale commodity chemical that is used primarily to manufacture polyvinyl acetate, an important component of paints, adhesives, and coatings. Vinyl acetate can be produced by the acetoxylation of ethylene, which involves the reaction of ethylene, oxygen and acetic acid in the presence of an activated palladium-gold catalyst. This process is generally performed in a gas phase, fixed bed tubular reactor, from which the resulting vinyl acetate is recovered by condensation and purification.
Through the years, there have been many efforts to increase the catalytic activity to reduce the amount of catalyst needed, driven by factors such as the high costs of the precious metals palladium and gold used in the catalyst. For example, U.S. Pat. No. 6,022,823 discloses generally calcining a support impregnated with palladium and gold salts prior to reducing the metals, which enhances catalyst activity.
Issues related to improving the overall efficiency and economics of the process remain, despite various advances in improving catalytic activity. Therefore, there is a need to identify new methods, catalyst compositions and properties, and process parameters that can further enhance the catalytic production of vinyl acetate monomer.